1. Field of the Invention
The present invention generally relates generally to an optical device. In particular, the invention relates to a block base having tree-structured groove arrays and a multi-core optical fiber block with a tree-structured groove array, and method for aligning optical fiber arrays in the multi-core optical fiber block.
2. Description of the Related Art
A multi-core optical fiber block is typically used for aligning an array of cores or strands of a multi-core optical fiber cable relative to an input or output terminal of a planar light wave circuit (PLC). The optical fiber block is also used as an input/output terminal of an optical device, such as a micro-optic device.
In general, a multi-core optical fiber block comprising a block base and a cover has been manufactured according to the following steps:
Step 1. seating an array of cores or strands of a multi-core optical fiber cable onto a plurality of V-shaped grooves, which are formed on a top surface of the block base made of silicon, quartz, glass or the like and which have a uniform pitch, depth and length, wherein the array of cores or strands of the multi-core optical fiber cable is typically prepared by partially removing a sheath from the multi-core optical fiber cable;
Step 2. covering the array of cores with a cover having a plurality of V-shaped grooves which are formed on a bottom surface of the cover and which have uniform pitch, depth and length;
Step 3. fixing the array of cores, the block base, and the cover using an adhesive such as epoxy resin; and
Step 4. polishing an end face of the block.
FIG. 1 is a schematic perspective view of a multi-core optical fiber block according to the prior art. FIG. 2 is a perspective of a block base of the multi-core optical fiber block shown in FIG. 1. FIG. 3 is a side view of the multi-core optical fiber block shown in FIG. 1. As shown in FIG. 1, a multi-core optical fiber block comprises first and second ribbon type multi-core optical fiber cables 110 and 140, respectively, a block base 170 and a cover 210.
The first and second ribbon type multi-core optical fiber cables 110 and 140, respectively, are layered horizontally, and have their respective sheaths 130 and 160 removed over a predetermined length at the end. The portions on which the sheaths 130 and 160 are removed from the first and second ribbon type multi-core optical fiber cables 110 and 140, respectively, are called first and second bare or de-sheathed multi-core optical fiber arrays 120 and 150, respectively.
Referring to FIG. 2, the block base 170 includes a body 180 which has a top surface formed with sixteen (16) V-shaped grooves 200 having a uniform pitch, depth and length, and a support 190 which extends from the body 180. In the sixteen V-shaped grooves 200 are seated the first and second de-sheathed multi-core optical fiber arrays 120 and 150, respectively, each of which consist of eight cores or strands.
Referring back to FIG. 1, the cover 210 has a bottom surface formed with sixteen V-shaped grooves 220 which have a uniform pitch, depth and length. The V-shaped grooves 220 serve to fix the first and second de-sheathed multi-core optical fiber_arrays 120 and 150, respectively, together with the corresponding V-shaped grooves 200 of the block base 170.
Referring to FIG. 3, it is apparent that the first and second de-sheathed multi-core optical fiber arrays 120 and 150 must be precisely aligned so that a height H1 of respective rhombic cavities formed by the V-shaped grooves 200 and 210 of the block base 170 and the cover 210 between both ends of the multi-core optical fiber block are uniform. However, as the first and second de-sheathed multi-core optical fiber arrays 120 and 150 aligned in the V-shaped grooves 200 of the block base 170 have a height(from the bottom surface of the block base 170) that is different from heights (from the bottom surface of the block base 170) of the first and second ribbon type multi-core optical fiber cables 110 and 140 during the alignment process, this alignment approach results in bending of the first and second de-sheathed multi-core optical fiber arrays 120 and 150. As a result, the first and second de-sheathed multi-core optical fiber arrays 120 and 150 deteriorate resulting in a decreased tensile strength breaking more easily upon any external force. Thus, there is a need to reduce bending of the first and second de-sheathed multi-core optical fiber arrays 120 and 150.
To reduce bending of the first and second de-sheathed multi-core optical fiber arrays 120 and 150, the first and second de-sheathed multi-core optical fiber arrays 120 and 150, respectively, are configured to extend at a predetermined length L1 from one end of the body 180 of the block base 170. This approach has some drawbacks. First, when the first and second multi-core optical fiber arrays 120 and 150, which extend from the layered first and second ribbon type optical fiber cables 110 and 140, are seated and fixed in the narrow shallow grooves 200 of the block base 170, it is difficult to simultaneously align the first and second multi-core optical fiber arrays 120 and 150 in the grooves 200 of the block base 170. Second, when the multi-core optical fiber arrays 120 and 150 extend at a predetermined length L1 from one end of the body 180 of the block base 170, and the multi-core optical fiber arrays have epoxy resin applied to respective portions which are not seated in the grooves 200 of the block base 170 to reduce bending of the multi-core optical fiber arrays 120 and 150, the epoxy resin is subjected to contraction or expansion as the portions applied with epoxy resin are widened. Due to this contraction and expansion, the multi-core optical fiber arrays 120 and 150 are subjected to a greater insertion loss as well as a higher possibility of breaking.